Research Projects

Native Pollinators in Michigan Blueberries

Julianna Tuell and Rufus Isaacs, in collaboration with Zachary Huang

Introduction

Most of Michigan’s food crops rely on pollination services to achieve economic yields. Managed colonies of honey bees (Apis mellifera) are typically rented to provide these services, but there is also significant potential for pollination services from a range of non-Apis species that are better adapted to forage on flowering crops in Michigan. Many of these species are better adapted for pollination of native North American crops, such as blueberry, squash, tomatoes etc. than the European honey bee. Identifying and measuring the abundance of these alternate pollinators is a key first step toward a better understanding of their potential role in Michigan agriculture. This will set the stage for future studies to understand how to conserve and enhance their populations under Michigan conditions, to provide a sustainable suite of pollinators that may help growers consistently achieve maximum yields.
Using blueberry as the focus crop, the long-term goal of this project is to identify candidates for future studies of pollinator conservation and enhancement to improve pollination under poor spring weather conditions, when honey bees are less active. This project will also provide leads for studies in other pollinator-dependent food crops.

Objectives:

1. Survey species diversity and abundance of pollinators in blueberry fields and nearby habitat.
2. Determine the relative importance of key pollinators for blueberry flowers using pollen identification.
3. Determine the relative contribution of Apis and non-Apis pollinators on blueberry fruit set and yield.

2003 Results

Objective 1. Survey species diversity and abundance of pollinators in blueberry fields and nearby habitat. Four commercial and four semi-abandoned blueberry fields were sampled for Apis and non-Apis bees throughout the season using timed visual observations. Alternative foraging plants found throughout the season surrounding blueberry fields were counted and their species richness was regressed against the abundance and diversity (Shannon-Weaver index) of non-managed bees observed on blueberry. There were significantly more Apis mellifera (honey bees) than non-Apis bees in the samples collected. There was no significant difference between commercial and semi-abandoned fields in bee abundance or diversity. Of the non-Apis bees, Halictid (sweat bees) were the most abundant, particularly on plants blooming in the perimeter of the blueberry fields.

Objective 2.

Determine the relative importance of key pollinators for blueberry flowers using pollen identification. Pollen samples were collected during 2003 and were mounted on microscope slides. These samples will be analyzed during the latter part of this winter.

Objective 3.

Determine the relative contribution of Apis and non-Apis pollinators on blueberry fruit set and yield. Flower clusters were bagged to prevent pollinator access. Bags were removed for pollinator visitation then replaced immediately after visitation until fruit set. Inclement weather, sparse blueberry bloom and low pollinator abundance at the site chosen were responsible for inconclusive results. A site better suited to the goal of Objective 3 has been chosen for FY-04, and results from this site will be included in the final report.

Project Funding

This is a two-year project and is being funded by a Project GREEEN grant.